HOPBFT: A Scalable and light weight Blockchain enabled Protocol for Securing Multi-Domain SDN

Software-Defined Networking (SDN) has transformed network management by decoupling control and data planes, enabling centralized control and programmability. However, this centralization introduces a critical single point of failure (SPoF) in the control plane, rendering the network vulnerable to breaches. The multi-controller architecture enhances scalability and resilience but complicates security management. Although challenges such as consensus delays and scalability persist, decentralized and tamper-proof blockchain ledgers offer a promising security solution for SDN. This paper proposes Hierarchical Optimized Practical Byzantine Fault Tolerance (HOPBFT), a novel consensus framework that integrates Raft-based intra-domain consensus with an optimized hierarchical Practical Byzantine Fault Tolerance (PBFT) inter-domain layer, enhanced by blockchain technology for improved security and coordination. Evaluated in a simulated multi-domain SDN environment using Mininet and Ryu controllers, HOPBFT outperforms the baselines (e.g., DLCA_R_P, Voting Based, Proof of Work) with 400 transactions per second (TPS) at 50 controllers, a latency of 340 ms, and a success rate of 96% compared to DLCA_R_P (160 TPS, 1170 ms, 91%). The communication complexity of HOPBFT is \(\:O\left(n\text{l}\text{o}\text{g}\:n\right)\) compared to traditional PBFT \(\:O\left({n}^{2}\right)\) to ensure scalability and efficiency. The key contributions of this study are a scalable consensus framework, an efficient two-phase agreement mechanism, and validated fault tolerance in multi-domain SDN settings.